This invention relates generally to gas generation, production or supply such as used in or in association with the inflation of inflatable devices such as inflatable vehicle occupant restraint airbag cushions used in vehicular inflatable restraint systems.
One particular aspect of this invention relates generally to the ignition of combustible materials and, more particularly, to the ignition of gas generant materials such as used in inflator devices used for the inflation of inflatable restraint airbag cushions.
It is well known to protect a vehicle occupant using a cushion or bag, e.g., an xe2x80x9cairbag,xe2x80x9d that is inflated or expanded with gas when the vehicle encounters sudden deceleration, such as in the event of a collision. In such systems, the airbag cushion is normally housed in an uninflated and folded condition to minimize space requirements. Upon actuation of the system, the cushion begins to be inflated in a matter of no more than a few milliseconds with gas produced or supplied by a device commonly referred to as an xe2x80x9cinflator.xe2x80x9d
Many types of inflator devices have been disclosed in the art for use in inflating one or more inflatable restraint system airbag cushions. Many prior art inflator devices include a solid form of gas generant material which is burned to produce or form gas used in the inflation of an associated airbag cushion.
Such inflator devices tend to involve rather complex ignition processes. For example, it is relatively common to employ an electrically initiated squib to ignite a separate charge of an igniter composition. The products of such ignition are then used to ignite the gas generant material. In practice, the ignition process of many various prior inflator devices require such a separate igniter charge because the squib does not itself generally supply sufficient hot gas, condensed phase particles or other ignition products to heat the gas generant material to result in the reaction of the material such as to result in desired gas generation.
FIG. 1 illustrates an inflator device or assembly generally designated by the reference numeral 10 and such as is known in the prior art. The inflator assembly 10 has a generally cylindrical external outline and includes a housing construction 12 such as formed of two structural components, i.e., a lower shell or base portion 14 and an upper shell or diffuser cap portion 16, such as may desirably be made of steel and appropriately joined or fastened together such as by application of an inertial welding operation. The housing 12 is illustrated in the general form of a flattened, disk-shaped circular cylinder typically or generally having a length to diameter ratio of about 0.5 or less. It will be appreciated that such a sized and shaped housing may most conveniently correspond to the shape of the vehicle steering wheel and can therefore facilitate assembly in an aesthetically pleasing manner.
The diffuser cap portion 16 is in the general form of an inverted bowl and includes a top wall 18 and a cylindrical sidewall 20. The sidewall 20 includes a plurality of spaced, preferably, generally uniformly spaced gas exit ports 22.
The base portion 14 includes a mounting opening 24, the use of which will be discussed in greater detail below. The base portion 14 also includes a peripheral bracket 28 that extends radially outward from the housing 12 and serves to form an interface attachment which is used to attach the inflator assembly 10 to a vehicle, the occupants of which are to be protected from injury such as may result from the impact of a collision.
The housing 12 is configured to define a generally cylindrical chamber 30. The chamber 30 contains or houses a supply of a gas generant material 32, such as composed of a pyrotechnic, such as known in the art, in a desired selected form. In FIG. 1, the gas generant 32 is shown as contained in the chamber 30 in a tablet form but other forms, such as known in the art may be used. Surrounding the gas generant material 32 is a filter assembly 34 such as includes a cooling screen or filter such as formed of multiple layers or wraps of metal screen.
The inflator assembly 10 also includes a retainer assembly 36 such as composed of a retainer 38 and annular-shaped diffuser and base damper pads, 40 and 42, respectively, and such as serving as construction expedients. For example, the inclusion of such a retainer assembly or specific components thereof may be useful and desired to retain the inflator assembly components in proper relative arrangement, prevent undesired gas flow passage through the assembly and/or minimize or avoid undesired contact of the gas generant within the assembly 10 such as may create undesired rattle or noise should the assembly be subjected to certain vibrations or other movements or forces. In practice, such damper pad elements are commonly composed or fabricated of a glass fiber material or the like.
Surrounding the filter 34 and generally adjacent the inner surface of the sidewall 20 is an adhesive-backed foil seal 44 which preferably hermetically seals the gas generant material 32 within the inflator 10, thereby protecting the gas generant material from possibly damaging ambient conditions, such as including moisture.
An igniter assembly, generally designated by the reference numeral 48, is mounted to the housing 12 in a location within the chamber 30 via the mounting opening 24. The igniter assembly 48 may take the form of a known pyrotechnic initiator device such as includes, as are known in the art, an igniter cup 50 having an interior 51 wherein is housed an igniter material 52, an igniter device or squib 54, and a squib adapter or holder 56 whereby the igniter assembly 48 is mounted to or mated with the housing 12. As shown, the igniter cup 50 and associated components of the igniter assembly 48 are inserted or fitted into or through an igniter tube 58. The igniter tube 58 can be formed of a gas-impermeable material, e.g., a metal such as plain carbon steel, and includes a plurality of spaced apart exit orifices 60 wherethrough products of ignition can be passed through and directed into contact with the gas generant material 32 to effect ignition and reaction thereof.
When actuated, the squib 54 causes ignition of the igniter material 52 which customarily results in an increase in pressure within the cup interior 51 with the subsequent predetermined rupturing or opening of the igniter cup 50 to permit passage, through the exit orifices 60, of ignition products produced by the combustion of the igniter material 52. With such passage, the ignition products are put into contact with the gas generant material 32 contained within the inflator chamber 30 such as to result in the ignition and reaction of the gas generant material 32. The gas generant material thus reacts to produce gas. The gas so produced passes through the filter 34, rupturing the foil seal 44 and passing through the gas exit ports 22 and out from the inflator assembly 10 into an associated airbag cushion (not shown). As will be appreciated, the contact of ignition products with the gas generant material can appropriately be, either or both, thermal or physical in nature.
In practice, the igniter assembly 48 can be formed by placing the igniter cup 50 containing the igniter material 52 over the igniter device/squib 54 and the holder 56. The igniter assembly 48 can be desirably placed at the mounting opening 24, such as with the igniter tube 58 in press fit relationship therewith, and joined to the housing 12 such as by welding the holder 56 to the base portion 14 at the mounting opening 24.
Such igniter charges have also been used in various dual stage or adaptive inflator assemblies. For example, FIG. 2 illustrates a dual stage or adaptive output inflator device or assembly generally designated by the reference numeral 210, such as generally disclosed in commonly assigned, co-pending U.S. patent application Ser. No. 09/465,082, the disclosure of which is hereby incorporated by reference. The inflator assembly 210 has various features in common with the inflator assembly 10, described above. In particular, the inflator assembly 210 has a generally cylindrical external outline and includes a housing construction 212 such as formed of a lower shell or base portion 214 and an upper shell or diffuser cap portion 216 and in the general form of a flattened, disk-shaped circular cylinder.
The diffuser cap portion 216 includes a top wall 218 and a cylindrical sidewall 220. The sidewall 220 includes a plurality of spaced gas exit ports 222. The base portion 214, in addition to a first mounting opening 224, however, also includes a second mounting opening 226. The base portion 214 includes a radially outward extending peripheral mounting or attachment bracket 228.
The housing 212 is configured to define a generally cylindrical first chamber 230 which contains or houses a supply of a first gas generant material 232, such as composed of a pyrotechnic. While the gas generant material 232 is shown in an extruded cylindrical perforated solid form, e.g., in the form of solids which include a cylindrical bore such that the gas generant material is generally tubular in shape, gas generant in other suitable forms can be used. Surrounding the gas generant material 232 is a filter assembly 234 such as includes a cooling screen or filter such as formed of multiple layers or wraps of metal screen.
The inflator assembly 210 also includes a retainer assembly 236 such as composed of a retainer 238, a diffuser damper pad 240 and a base damper pad 242. A foil seal 244, generally adjacent the inner surface of the sidewall 220, seals the gas generant material 232 within the inflator 210.
A first igniter assembly, generally designated by the reference numeral 248 and similar to the igniter assembly 48 described above, is mounted to the housing 212 in a location within the first chamber 230 via the mounting opening 224. The first igniter assembly 248 includes an igniter cup 250 having an interior 251 wherein is housed a supply of igniter material 252, an igniter device or squib 254, and a squib adapter or holder 256 whereby the igniter assembly 248 is mounted to or mated with the housing 212. The igniter cup 250 and associated components of the igniter assembly 248 are inserted or fitted into or through an igniter tube 258. The igniter tube 258, similar to the igniter tube 58 includes exit orifices (not shown) wherethrough products of ignition can be passed through and directed into contact with the gas generant material 232 to effect ignition and reaction thereof.
The first chamber 230 also houses or contains a second chamber 262. It is with respect to this second chamber and the construction and operation thereof that the inflator assembly 210 differs most significantly from the inflator assembly 10 described above. The second chamber 262 includes a generant cup 264, a lid closure 265, a second igniter device or squib 266, and a second squib adapter 268 whereby the second chamber 262 is mounted to or mates with the housing 212 at the second mounting opening 226.
The generant cup 264 and the lid closure 265 cooperate to form a generant cup interior 270 wherein desirably placed is a selected quantity of a second gas generant material 272. The second gas generant material 272 may typically be in the form of a pyrotechnic material and may be either the same or different in composition, shape, size or form, as compared to the first gas generant material 232.
The generant cup 264 desirably includes a generally cylindrical sidewall 274 and such as preferably includes a shoulder portion 276 such as formed therein. The lid closure 265 and the shoulder portion 276 may desirably form a press or interference fit form of attachment when in a static state or condition. The generant cup 264 and the lid closure 265 cooperate and function in a manner such as to prevent the combustion products resulting upon actuation of the first igniter device 254, to enter into the second chamber 262. Further, the generant cup 264 and the lid closure 265 desirably cooperate and function in a manner such as to permit the combustion products formed by reaction of the gas generant material contained within the second chamber 262, when properly and desirably actuated, to pass from the second chamber 262 out into the first chamber 230 and subsequently through the filter assembly 234 and out through the exit ports 222 into an associated airbag cushion (not shown).
For example, in a typical deployment operation involving actuation and firing of the second chamber 262, actuation of the second igniter squib 266 results in sufficient discharge to ignite at least some of the second gas generant material 272. The ignition and reaction of the second gas generant material in turn produces or results in sufficient pressure within the second chamber 262 to dislodge the lid closure 265 from the shoulder portion 276 such as to open the second chamber 262 to entry of combustion products formed by or as a result of actuation of the first chamber 230. Entry into the second chamber of such combustion products desirably can result in the more complete or full combustion of the remaining second gas generant material.
A common means of obtaining substantially simultaneously ignition of an extended length of an igniter composition charge is by means of an ignition cord. In practice, however, it is common that such a length of ignitor cord be housed or contained within an igniter tube extending within such an igniter charge.
While ignition of a gas generant material may ultimately be achieved through such an inclusion and use of an igniter charge, such assemblies and associated uses tend to undesirably complicate the ignition process as well as to complicate the manufacture, production and design of the associated inflator device. For example, such uses typically necessitate the manufacture of a container or other storage device to hold or store the igniter composition and then the incorporation of such a storage container in the inflator device. As will be appreciated, the incorporation and use of such an ignition process can detrimentally impact either or both the weight and cost of the corresponding apparatus hardware. Further, space is often at a premium in modern vehicle design. Consequently, it is generally desired that the space requirements for various vehicular components, including inflatable vehicle occupant restraint systems, be reduced or minimized to as great an extent as possible. The incorporation of an igniter assembly such as described above and associated support structures, may require a larger than desired volume of space within an associated inflator device. In particular, such volume of space could potentially be utilized to store or contain gas generant material and thereby permit the volume of space required by the inflator device to be reduced.
Thus, there is a need and a demand for alternative airbag inflator device ignition schemes and, in particular, there is a need and a demand for avoiding the requirement or inclusion of separate igniter composition charges and associated ignition trains or hardware. One approach discussed in the prior art has been to apply a coating of an igniter formulation directly on a gas generant material. For example, various patents, including U.S. Pat. Nos. 4,698,107; 4,806,180; and 5,034,070, disclose processing wherein an ignition coating is applied, such as in the form of a liquid or a water slurry, to azide-based gas generant materials. Such processing typically necessitates first the formation of the azide-based gas generant, including the proper forming and drying of gas generant grains in selected shapes, followed by the coating of the grains with a wet slurry of the ignition material, such as by immersion of the grains in a slurry of the coating material, and then final drying.
In such dip coat processing, generally either individual gas generant tablets or wafers are coated as they go through a coating slurry on a conveyer belt, or the gas generant tablets or wafers are put in bulk containers and submerged in the slurried coating material. These types of process are typically relatively slow and may lead to problems such as coated tablets/wafers sticking either or both to themselves and associated equipment, such as conveyer belts.
In addition, dependent on the shape of the gas generant tablet or wafer there may also be a problem in obtaining application of a uniform coating. For example, if the gas generant material has a relatively flat form, the slurry coating may tend to pool and may therefore dry to form a coating of variable thicknesses.
Also, dip coating equipment (e.g., dip baskets and conveyer belts) may easily be contaminated with igniter material, leading to potential or increased safety concerns.
In view of the above, there is a need and a demand for materials and processing techniques such as may facilitate or permit the inclusion of an igniter composition within an inflator device, such as the placement of an ignition composition onto a gas generant material having a selected form or to a non-gas generant surface within an inflator device, for example.
As identified above, many types of inflator devices have been disclosed in the art for use in the inflation of one or more inflatable restraint system airbag cushions. A common form or type of prior art inflator device includes gas generant material in a solid form and which solid gas generant material is burned to produce or form gas used in the inflation of an associated airbag cushion. For example, such inflators can generally produce or derive inflation gas via the combustion of a solid form gas generating material, i.e., a pyrotechnic. In practice, however, such gas generating materials can typically produce various undesirable combustion products, including various solid particulate materials. The removal of such solid particulate material, such as by the incorporation of various filtering devices within or about the inflator, can undesirably increase inflator design and processing complexity and can increase the costs associated therewith. In addition, the temperature of the gases emitted from such inflator devices can typically vary between 500xc2x0 F. (260xc2x0 C.) and 1200xc2x0 F. (649xc2x0 C.), dependent upon numerous interrelated factors including the desired level of inflator performance, as well as the type and amount of gas generant materials used. Consequently, airbag cushions used in conjunction with such inflator devices are commonly constructed of or coated with special materials which are resistant to such high temperatures. As will be appreciated, such specially fabricated or prepared airbag cushions typically are more costly to manufacture and produce.
Another category of inflator devices disclosed in the art for the inflation of one or more inflatable restraint system airbag cushions is often referred to as xe2x80x9ccompressed gas inflatorsxe2x80x9d and refers to various inflators which contain a selected quantity of compressed gas. For example, one particular type of compressed gas inflator, commonly referred to as a xe2x80x9cstored gas inflator,xe2x80x9d simply contains a quantity of a stored compressed gas which is selectively released to inflate an associated airbag cushion.
A second type of compressed gas inflator, commonly referred to as a xe2x80x9chybrid inflator,xe2x80x9d typically supplies or provides inflation gas as a result of a combination of stored compressed gas with the combustion products resulting from the combustion of a gas generating material, e.g., a pyrotechnic.
In the past, compressed gas inflators of various types have commonly been at a disadvantage, as compared to pyrotechnic inflators, in terms of size, weight and/or cost. This is especially significant in view of the general design direction toward relatively small, lightweight and economical modern vehicle components and assemblies. Thus, there is a continuing need and demand for further improved apparatus and techniques for inflating inflatable devices such as inflatable airbag cushions.
A more recently developed inflator device is at least in part the subject of commonly assigned Rink, U.S. Pat. No. 5,669,629, issued Sep. 23, 1997; Rink et al., U.S. Pat. No. 5,884,938, issued Mar. 23, 1999; and Rink et al., U.S. Pat. No. 5,941,562, issued Aug. 24, 1999, the disclosures of which patents are hereby and expressly incorporated herein in their entirety. In one form of such recently developed inflator device, inflation gas is produced or formed, at least in part, via the decomposition or dissociation of a selected gas source material, such as in the form of a compressed gas and such as via the input of heat from an associated heat source supply or device. Such an inflator device is sometimes referred to as a xe2x80x9cdissociative inflator.xe2x80x9d
While compressed gas inflators and dissociative inflators have been generally successful in overcoming at least some of the problems or shortcomings associated with prior types or forms of inflator devices, further improvements are desired and are being sought. In particular, there is a need and a desire for inflator devices which while containing an expandable fluid effective to provide a gaseous inflation medium also advantageously employs or incorporates a pyrotechnic material such as to augment or enhance such gaseous inflation medium.
A general object of at least one aspect of the invention is to provide improved igniter compositions, inflator devices and methods for including an igniter material within an inflator device.
A more specific objective of the invention is to overcome one or more of the problems described above.
A general object of the invention can be attained, at least in part, through an improvement in igniter compositions used to ignite a gas generant material within an inflator device. As detailed below, such improvement in accordance with one embodiment of the invention involves including, in the igniter composition, a binder additive, e.g., such as a silicone resin, effective to adhere the igniter composition to a surface within the inflator device.
The prior art generally fails to provide inflator device assemblies and igniter compositions useable therein which can operate as effectively as may be desired without including or requiring additional hardware such as igniter tubes, igniter cup assemblies or the like to hold or contain such igniter materials. At least partially as a result thereof, the prior art has generally failed to provide inflator device assemblies having a design of one or more of desired simplicity of construction and/or operation, reduced weight and reduced cost.
The invention further comprehends an improvement in an airbag inflator device which contains a quantity of gas generant material reactable to produce gas for inflation of an associated inflatable device and a quantity of an igniter material reactable to ignite at least a portion of the quantity of gas generant material. In accordance with one preferred embodiment of the invention, such improvement relates to the inclusion within the inflator device of a damper pad onto which pad at least a portion of the quantity of igniter material forms a coating.
The invention still further comprehends a method of including an igniter material within an inflator device. Such method, in accordance with one preferred embodiment of the invention, involves applying an igniter material composition which includes an igniter fuel, an igniter oxidizer and a binder additive effective to adhere the igniter material composition to an inner surface of the inflator device.
The invention yet still further comprehends a method of providing an igniter material for inclusion within an inflator device which contains at least one damper pad. In particular, such method includes coating a damper pad substrate with an igniter material composition which includes an igniter fuel, an igniter oxidizer and an additive effective to adhere the igniter material composition to the damper pad substrate.
Another general object of the invention can be attained, at least in part, through an inflator device which includes a closed storage chamber having contents including a quantity of an expandable fluid effective to provide a gaseous inflation medium. The inflator device also includes at least one exit opening wherethrough at least a portion of the gaseous inflation medium provided by the inflator device can exit the inflator device. The inflator device further includes an initiator device effective upon actuation to open the storage chamber and place at least a portion of the storage chamber contents in fluid communication with the at least one exit opening. In accordance with one preferred embodiment of the invention, a quantity of a pyrotechnic composition is disposed on a non-gas generant surface within the inflator device and which pyrotechnic composition is reactable upon initiation from the initiator device to augment at least one fill characteristic of the gaseous inflation medium. The pyrotechnic composition desirably includes a binder additive, such as a silicone resin, effective to adhere the pyrotechnic composition to a desired surface, e.g., a target surface, within the inflator device.
The prior art generally fails to provide inflator devices which while containing an expandable fluid effective to provide a gaseous inflation medium also includes a pyrotechnic material to enhance one or more fill characteristic of the gaseous inflation medium and wherein the pyrotechnic material is incorporated within the inflator in an as simple and effective a manner as may otherwise be desired.
The invention further comprehends an inflator device which includes a closed storage chamber which contains a dissociative gas source material fluid under an elevated pressure and which dissociative gas source material fluid is adapted to at least in part form a gaseous inflation medium. The inflator device also includes at least one exit opening wherethrough at least a portion of the gaseous inflation medium provided by the inflator device can exit the inflator device. The inflator device further includes an initiator device effective upon actuation to open the storage chamber, initiate dissociation of at least a portion of the dissociative gas source material to at least in part form a gaseous inflation medium, and place at least a portion of the gaseous inflation medium in fluid communication with the at least one exit opening. A quantity of a pyrotechnic composition is disposed on a non-gas generant surface within the inflator device and which pyrotechnic composition is reactable upon initiation from the initiator device to at least heat the gaseous inflation medium such as to initiate dissociation of at least a portion of the dissociative gas source material. In accordance with one preferred embodiment of the invention, both the at least one exit opening and the initiator device are disposed on a first end of the inflator device.
As used herein, references to an xe2x80x9cexpandable fluidxe2x80x9d and the like are to be understood to refer to fluids such as when employed in inflator devices can be expanded to form a gaseous inflation medium. As will be appreciated, such fluids are typically present in an inflator device in a gaseous, liquid, or multi-phase form (i.e., a partially liquid and partially gaseous mixture). Expandable fluids can, for example, include one or more of a) an inert material such as one or more noble gases such as argon and helium, for example, b) materials such as nitrogen and carbon dioxide which are essentially inert under such processing conditions and c) dissociative gas source materials, such as nitrous oxide, for example, or various combinations thereof.
References to a xe2x80x9cfill characteristicxe2x80x9d or the like of a gaseous inflation medium resulting from an inflator device generally refers to one or more of the volume, amount and quantity of gas provided or resulting from the device. For example, as detailed below, augmentation of a fill characteristic of the gaseous inflation medium in accordance with the invention may involve reaction of a pyrotechnic composition to heat the gaseous inflation medium, provide additional gaseous reaction products or both.
The references to xe2x80x9cdissociation,xe2x80x9d xe2x80x9cdissociation reactionsxe2x80x9d and the like are to be understood to refer to the dissociation, splitting, decomposition or fragmentation of a single molecular species into two or more entities.
xe2x80x9cThermal dissociationxe2x80x9d is a dissociation controlled primarily by temperature. It will be appreciated that while pressure may, in a complex manner, also influence a thermal dissociation such as perhaps by changing the threshold temperature required for the dissociation reaction to initiate or, for example, at a higher operating pressure change the energy which may be required for the dissociation reaction to be completed, such dissociation reactions remain primarily temperature controlled.
An xe2x80x9cexothermic thermal dissociationxe2x80x9d is a thermal dissociation which liberates heat.
xe2x80x9cEquivalence ratioxe2x80x9d (xcfx86) is an expression commonly used in reference to combustion and combustion-related processes. Equivalence ratio is defined as the ratio of the actual fuel to oxidant ratio (F/O)A divided by the stoichiometric fuel to oxidant ratio (F/O)S:
xcfx86=(F/O)A/(F/O)Sxe2x80x83xe2x80x83(1) 
(A stoichiometric reaction is a unique reaction defined as one in which all the reactants are consumed and converted to products in their most stable form. For example, in the combustion of a hydrocarbon fuel with oxygen, a stoichiometric reaction is one in which the reactants are entirely consumed and converted to products entirely constituting carbon dioxide (CO2) and water vapor (H2O). Conversely, a reaction involving identical reactants is not stoichiometric if any carbon monoxide (CO) is present in the products because CO may react with O2 to form CO2, which is considered a more stable product than CO.)
For given temperature and pressure conditions, fuel and oxidant mixtures are flammable over only a specific range of equivalence ratios. Mixtures with an equivalence ratio of less than 0.25 are herein considered nonflammable, with the associated reaction being a decomposition reaction or, more specifically, a dissociative reaction, as opposed to a combustion reaction.
References herein to a xe2x80x9cpyrotechnicxe2x80x9d material, refer to a material which in its simplest form, consists of an oxidizing agent and a fuel that produce an exothermic, self-sustaining reaction when heated to the ignition temperature thereof.
References herein to a material or pyrotechnic composition or the like as being xe2x80x9cfuel-richxe2x80x9d or xe2x80x9crich in fuelxe2x80x9d generally refers to such material as contains or includes fuel in a relative amount, as compared to the amount of oxidizer therein contained, in excess of the theoretical stoichiometric amount which will undergo complete combustion, based on the amounts of fuel and oxidizer therein contained.
References to the detection or sensing of xe2x80x9coccupant presencexe2x80x9d are to be understood to refer to and include detection and sensing of one or more of the size, weight, and/or positions of a particular occupant under consideration.
References to an xe2x80x9cadaptivexe2x80x9d inflation system and the like are to be understood to refer to inflatable device inflation wherein selected inflatable devices are inflated or inflated in a manner generally dependent on selected operating conditions such as one or more of ambient temperature, occupant presence, seat belt usage, seat position of the occupant and rate of deceleration of the motor vehicle, for example.
References herein to an inflator device as being a xe2x80x9creverse flowxe2x80x9d inflator are to be understood to generally refer to inflator devices wherein the exit area and the initiator device are both disposed on the same end of the inflator device.
Other objects and advantages will be apparent to those skilled in the art from the following detailed description taken in conjunction with the appended claims and drawings.